This invention relates to a fluid delivery apparatus, and more particularly, to a fluid-delivery apparatus with a bellowed ampoule.
Syringes that utilize expandable encasements are known. See for example, U.S. Pat. No. 4,073,288 to Chapman and U.S. Pat. No. 5,147,311 to Pickhard. Such traditional syringes, however, do not compensate for the effect of encroachment on the bulk fluid volume within the syringe due to movement of the encasement walls.
According to the present invention a fluid-delivery apparatus for delivering a medicament to a patient is provided, which accounts for the effect of encroachment that occurs as the fluid is-delivered therefrom. This apparatus comprises a housing defining a passageway, a bellowed ampoule positioned to lie in the passageway of the housing, the bellowed ampoule including a body having first and second ends and formed to define a cavity configured to contain the medicament, and a piston. The piston is positioned in the housing and formed to press the second end of the ampoule toward the first end. In addition, the apparatus further comprises a visible non-linear scale representing the relationship between a volume of medicament delivered from the first end of the ampoule and a distance that the piston has traveled in the housing toward the first end.
In accordance with another embodiment of the present invention a fluid-delivery apparatus for delivering a uniform volume of medicament to a patient is provided. The apparatus comprises a housing defining a passageway, a bellowed ampoule positioned to lie in the passageway of the housing, a piston, and a piston-drive system. The bellowed ampoule includes first and second ends and defines a cavity configured to contain the medicament. The piston is formed for movement in the housing to press the second end of the ampoule toward the first end. Further, the piston-drive system adjusts the movement of the piston in the housing so that the medicament is delivered in uniform increments from the first end of the ampoule.
Still further in accordance with another embodiment of the present invention, a method for determining the amount of fluid delivered from a bellowed ampoule positioned in a cylindrical housing having a radius of r0 that is substantially equal to an outermost radius of the ampoule is provided. The method comprises the steps of calculating the relative encroachment function Err of the bellowed ampoule from the equation
Err=xcexa8xc2x7(1xe2x88x92xcexa8/3), where xcexa8xe2x89xa1(c/r0){square root over (1xe2x88x92(z/c)2)},
z is the height of one half-fold of one bellow of the ampoule, and c is length of an upper panel of one bellow, depressing the ampoule a pre-determined distance in the housing changing the height z of one half-fold of one bellow, and determining the cumulative volume dispensed Vd from the bellowed ampoule. The cumulative volume dispensed is determined from the equation
Vd=V0xe2x88x92(xcfx80r02nz)xc2x7[1xe2x88x92Err],
where V0 is the initial volume of the filled reservoir and n is the number of half folds in the bellowed ampoule.
In addition, in accordance with the present invention a method for delivering a constant linear volume of fluid from a bellowed ampoule positioned in a cylindrical housing having a radius of r0 that is substantially equal to an outermost radius of the ampoule is provided. The method comprises the steps of calculating the relative encroachment function Err of the bellowed ampoule from the equation
Err=xcexa8xc2x7(1xe2x88x92xcexa8/3), where xcexa8xe2x89xa1(c/r0){square root over (1xe2x88x92(z/c)2)},
z is the height of one half-fold of one bellow of the ampoule, and c is length of an upper panel of one bellow, determining the cumulative volume dispensed Vd from the bellowed ampoule from the equation
Vd=V0xe2x88x92(xcfx80r02nz)xc2x7[1xe2x88x92Err],
where V0 is the initial volume of the filled reservoir and n is the number of half folds in the bellowed ampoule, and compressing the ampoule in the housing at a rate sufficient to achieve a constant linear flow of fluid from the ampoule in accordance with the equation             ⅆ      z        /          ⅆ              V        d              =                    (                              -            π                    ⁢                      xe2x80x83                    ⁢                      n            ·                          [                                                                    r                    0                    2                                    ·                                      [                                          1                      -                      Err                                        ]                                                  +                                                      (                                                                  1                        +                                                  2                          ⁢                                                      xe2x80x83                                                    ⁢                                                      ψ                            /                            3                                                                                              ψ                                        )                                    ·                                      z                    2                                                              ]                                      )                    -        1              .  
Additional features of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.